Well it shouldn't have stopped mid way. 39 is still 20 away from 59, so I should of been able to continue, just at a slower pace. I understand how leveling works, I'm just pondering why I stopped gaining EXP halfway.

For all you Legends out there, try doing the 'Dys-Geni-c Chaorruption?' quest from Cleric Dawn. You just need to kill Ultra-Tibi once for 10k EXP. With boosts it gives you 20k and with a full room you can level up real easy. Got from 55 to 60 in about 2 hours.